File Expression Language

File language is now merged with Simple language

From Camel 2.2: the file language is now merged with Simple language which means you can use all the file syntax directly within the simple language.

The File Expression Language is an extension to the Simple language, adding file related capabilities. These capabilities are related to common use cases working with file path and names. The goal is to allow expressions to be used with the File and FTP components for setting dynamic file patterns for both consumer and producer.

Syntax

This language is an extension to the Simple language so the Simple syntax applies also. So the table below only lists the additional. By contrast to the Simple language, the File Language also supports the use of Constant expressions to enter a fixed filename, for example.

All the file tokens use the same expression name as the method on the java.io.File object. For example: file:absolute refers to the java.io.File.getAbsolute() method.

Note: not all expressions are supported by the current Exchange. For example, the FTP component supports some of the options, whereas the File component supports all of them.

Expression

Type

File Consumer

File Producer

FTP Consumer

FTP Producer

Description

date:command:pattern

String

yes

yes

yes

yes

For date formatting using the java.text.SimpleDateFormat patterns which is an extension to the Simple language.

Additional command is: file (consumers only) for the last modified timestamp of the file.

Refers to the file name (is relative to the starting directory, see note below).

file:name.ext

String

yes

no

yes

no

Camel 2.3: refers to the file extension only.

file:name.ext.single

String

yes

no

yes

no

Camel 2.14.4/2.15.3: refers to the file extension. If the file extension has multiple dots, then this expression strips and only returns the last part.

file:name.noext

String

yes

no

yes

no

Refers to the file name with no extension (is relative to the starting directory, see note below).

file:name.noext.single

String

yes

no

yes

no

Camel 2.14.4/2.15.3:refers to the file name with no extension (is relative to the starting directory, see note below). If the file extension has multiple dots, then this expression strips only the last part, and keep the others.

file:onlyname

String

yes

no

yes

no

Refers to the file name only with no leading paths.

file:onlyname.noext

String

yes

no

yes

no

Refers to the file name only with no extension and with no leading paths.

file:onlyname.noext.single

String

yes

no

yes

no

Camel 2.14.4/2.15.3: refers to the file name only with no extension and with no leading paths. If the file extension has multiple dots, then this expression strips only the last part, and keep the others.

file:parent

String

yes

no

yes

no

Refers to the file parent.

file:path

String

yes

no

yes

no

Refers to the file path.

file:size

Long

yes

no

yes

no

Camel 2.5: refers to the file length returned as a Long type.

File Token Example

Relative Paths

We have a java.io.File handle for the file hello.txt in the following relative directory: .\filelanguage\test. And we configure our endpoint to use this starting directory .\filelanguage.

The file tokens returned are:

Expression

Returns

file:absolute

false

file:absolute.path

\workspace\camel\camel-core\target\filelanguage\test\hello.txt

file:ext

txt

file:name

test\hello.txt

file:name.ext

txt

file:name.noext

test\hello

file:onlyname

hello.txt

file:onlyname.noext

hello

file:parent

filelanguage\test

file:path

filelanguage\test\hello.txt

Absolute Paths

We have a java.io.File handle for the file hello.txt in the following absolute directory: \workspace\camel\camel-core\target\filelanguage\test. And we configure out endpoint to use the absolute starting directory: \workspace\camel\camel-core\target\filelanguage.

Examples

Lets assume we use the file consumer to read files and want to move the read files to backup folder with the current date as a sub folder. This can be achieved using an expression like:

relative folder names are also supported so suppose the backup folder should be a sibling folder then you can append .. as:

As this is an extension to the Simple language we have access to all the goodies from this language also, so in this use case we want to use the in.header.type as a parameter in the dynamic expression:

If you have a custom Date you want to use in the expression then Camel supports retrieving dates from the message header.

And finally we can also use a bean expression to invoke a POJO class that generates some String output (or convertible to String) to be used:

And of course all this can be combined in one expression where you can use the File Language, Simple and the Bean language in one combined expression. This is pretty powerful for those common file path patterns.

In Camel you can use the File Language directly from the Simple language which makes a Content Based Router easier to do in Spring XML, where we can route based on file extensions as shown below:

If you use the fileName option on the File endpoint to set a dynamic filename using the File Language then make sure you use the alternative syntax (available from Camel 2.5) to avoid clashing with Spring's PropertyPlaceholderConfigurer.

bundle-context.xml

bundle-context.cfg

Notice how we use the $simple{} syntax in the toEndpoint above. If you don't do this, they will clash and Spring will throw an exception: